General or local administration of an active drug through integument or mucous membrane is usually conducted by applying thereto a solution of a drug in a solvent, by applying as a creamy ointment obtained by mixing a drug with a soft material, or by inserting or embedding such in the form of suppository or tablet.
One of the inevitable defects with these administration methods is that, though the drug level in a circulatory system is raised each time a drug is administered, the drug level in blood or in a particular part of body decreases in a short time, thus being not maintained at a constant level.
In order to solve this defect, approaches have been developed for continuously administering an active drug, generally or locally, through integument or mucous membrane, which have been attempted to be practiced.
One of such approaches is a pressure-sensitive, adhesive administration tape or film which comprises a carrier having provided thereon a pressure-sensitive, adhesive composition containing an active drug added thereto. This administration tape or film enables continuous administration of the active drug, because the adhesive composition effectively prevents the drug from being released onto the skin surface all at one time. However, the quantity of the administered drug decreases with time. Thus such tape or film fails to continuously administer the drug at a constant rate.
Another approach is a drug administration material comprising a stratum consisting of a backing material, a drug-retaining layer, a polymeric film layer which controls a drug migration rate, and a pressure-sensitive, adhesive layer. This material allows a drug contained therein to diffuse and permeate through the polymeric film layer and the pressure-sensitive, adhesive layer to the skin surface. However, since control of the drug diffusion and migration rate is conducted by controlling the diffusion rate in the polymeric material, additional factors are involved which control permeation of the drug in both the polymeric film and the adhesive layer. Thus, the kinds of the polymeric material and the adhesive must be properly selected depending upon the structure of a drug, and also with consideration for the adhesiveness of the adhesive to skin. Such complexity with the drug administration material has made the application of such to various drugs difficult.